The enormous variety of biochemical reactions that comprise life are nearly all mediated by a series of biological catalysts known as enzymes. Enzymes are proteins which possess specific properties that enable them to catalyze a series of reactions, allowing metabolic pathways to degrade and to reconstruct products needed to maintain organisms. By the binding of substrates through geometrically and physically complementary reactions, enzymes are stereospecific in binding substrates as well as in catalyzing reactions. The stringency for this stereospecificity varies as some enzymes are more specific to the identity of their substrates, while others are capable of binding multiple substrates and can catalyze numerous types of reactions.
Examples of enzymes include, for example, carboxylases, fatty acid desaturases, serine/threonine dehydratases, hexokinases, peptidyl tRNA hydrolases, dual specificity phosphatases, phospholipases and transporters. Such enzymes have the ability to, for example: (1) hydrolyze an ester linkage and/or liberate the free acid form of a substrate, e.g., hydrolysis of a triglyceride and/or liberation of free fatty acid(s) and glycerol; (2) catalyze the formation of a double bond, preferably, at positions up to 9 carbons from the carboxyl end of a molecule, e.g., a fatty acid, such as a polyunsaturated fatty acid; (3) catalyze the phosphorylation of a sugar, e.g., an aldohexoses and a ketohexoses (e.g., glucose, mannose, fructose, sorbitol and glucosamine); (4) catalyze sugar metabolism; (5) transfer a phosphate from a phosphate donor (e.g., ATP) to a sugar, e.g., an aldohexoses and a ketohexoses (e.g., glucose, mannose, fructose, sorbitol and glucosamine) to form a phosphorylated sugar, e.g., glucose-6-phosphate; (6) catalyze the removal of a phosphate group attached to a tyrosine residue in a protein target, e.g., a growth factor receptor; (7) catalyze the removal of a phosphate group attached to a serine or threonine residue in a protein e.g., a growth factor receptor; (8) hydrolyze covalent bond between peptide and tRNA within peptidyl-tRNAs; (9) catalyze the hydrolysis of phosphatidyl-inositol-4,5-bisphosphate (PIP2) producing diacylglycerol and inositol 1,4,5-trisphosphate; (10) transport of a substrate or target molecule (e.g., a Ca2+ ion) from one side of a biological membrane to the other; and (11) be phosphorylated or dephosphorylated. Accordingly, there exits a need to identify additional human enzymes, for example, for use as disease markers and as targets for identifying various therapeutic modulators.